1. Field of the Invention
The present invention relates to a valve apparatus and a water heating apparatus including the same.
2. Description of the Background Art
A water heating apparatus is provided with a valve apparatus for adjusting a ratio of distribution to a bypass circuit and a heat exchanger. For example, Japanese Patent Laying-Open No. 4-141709 describes a valve apparatus. The valve apparatus described in this publication is a mixing valve having a valve shaft to which a valve element for hot water and a valve element for water are attached in a mixing chamber connected to both of a hot water flow path and a water flow path. By moving this valve shaft in an axial direction by rotation, opening of the valve element for hot water with respect to a valve seat for hot water and opening of the valve element for water with respect to a valve seat for water are adjusted to thereby control a ratio of mixing hot water and water.
With the valve apparatus described in the publication above, however, in order to control a ratio of mixing hot water and water, the valve shaft should be moved in the axial direction by rotating the valve shaft. Therefore, the valve shaft should be threaded and the valve shaft should be large in thickness. Thus, an O-ring to be fitted to an outer circumference of the valve shaft should also be large in size for use. Therefore, since resistance caused by the O-ring during rotation of the valve shaft is high, sliding torque becomes great. A large-sized motor is thus required for rotating the valve shaft, which may result in a large-sized and complicated apparatus.